This invention relates to the joining of articles together and, more particularly, to the alignment of articles that are to be joined.
In one type of manufacturing process, two articles are prepared separately, fitted together in a male/female joint, and brazed. The procedure may be extended to the assembly and brazing of multiple parts to each other, either simultaneously or sequentially. An example of interest to the inventors is the sequential assembly and brazing of a combustor dome assembly of an aircraft gas turbine engine. Multiple swirler/spectacle plate/deflector assemblies are brazed together, and then the multiple swirler/spectacle plate/deflector assemblies are brazed to the combustor dome.
In each case, a male inserted surface is dimensioned to be received into a female recess, with a sufficient clearance to provide for a subsequent brazed joint. A combination of fixturing and tack welding is used to hold the male part in a specific required relation to the female part. The assembly of parts and fixturing is heated in an oven to a temperature above the melting point of the braze metal The braze metal is drawn up into the clearance space between the male inserted surface and the female recess by capillary action. When the assembly is cooled, the braze metal solidifies to join the parts together. The fixturing is thereafter removed.
While operable and widely used, this approach has the drawback that complex fixturing may be required, which is time consuming to fabricate, install, and remove. In the case described above, there are multiple swirlers and deflectors to be assembled, each requiring careful assembly and alignment of the fixturing. If the fixturing should be installed with a slight misalignment of the parts, or if the fixturing shifts during the heating of the parts in the furnace during the brazing cycle, the final result is misalignment of the brazed parts and necessary rework if alignment tolerances are exceeded. Tack welds may also be used between the parts to be brazed and/or between the fixturing and the parts, which involves the initial welding cost. Additionally, it is often the case that even careful fixturing alignment leaves a nonuniform clearance around the circumference of the male inserted surface, so that the completed braze joint is slightly nonuniform. The clearance between the parts must be sufficient to ensure that the braze metal can flow into the clearance gap, which may result in even further misalignments of the parts and nonuniformity of the braze joint.
There is a need for an improved approach to the manufacturing of braze assemblies and other joined assemblies, where the joining material lies between the parts to be joined. The present invention fulfills this need, and further provides related advantages.
The present invention provides an assembly of parts that are joined together by a joining material that is disposed between the parts, and a method for preparing the assembly of parts. The approach of the invention does not require fixturing or tack welding, or a change in the configuration of the parts, yet holds the parts carefully and precisely in the desired orientation. The clearance between the male inserted surface and the female recess may be made uniform prior to joining, resulting in a uniformly thick joint. The approach of the invention may be used with a wide variety of types of parts to be joined, and in both simultaneous and sequential joining of assemblies with more than two parts.
An assembly of parts comprises a female part having a recess therein with a recess surface, and a male part having an inserted surface received within the recess of the female part. There is a relief pattern on at least one of the recess surface and the inserted surface. The recess surface, the inserted surface, and the relief pattern are dimensioned such that the inserted surface is received within the recess with a contacting-channeled fit between the inserted surface and the recess surface. A joining material joins the inserted surface to the recess surface, with the joining material disposed within a relief volume of the relief pattern. The joining material preferably comprises a quantity of joining metal such as braze metal disposed within the relief volume.
Preferably, the relief pattern is on the inserted surface. The relief pattern has a relief dimension (i.e., relief depth) of not less than about 0.001 inch, preferably from about 0.001 to about 0.010 inches, and most preferably from about 0.001 to about 0.007 inch. The recess surface is substantially cylindrical. The relief pattern preferably comprises a knurl pattern, such as a diamond knurl pattern or a straight knurl pattern. Desirably, the male part and the female part are components of a gas turbine engine.
A method for preparing an assembly of parts comprises the steps of providing a female part having a recess therein, the recess having a recess surface, and providing a male part having an inserted surface receivable within the recess of the female part. A relief pattern is formed on at least one of the recess surface and the inserted surface, preferably extending substantially around the entire lateral periphery of the surface. The recess surface, the inserted surface, and the relief pattern are dimensioned such that the inserted surface is received within the recess with a contacting-channeled fit between the inserted surface and the recess surface. The inserted surface of the male part is inserted into the recess of the female part, and the inserted surface of the male part is joined to the recess surface of the female part with a joining material disposed within a relief volume of the relief pattern.
The relief pattern, preferably in the form of knurling, in conjunction with the contacting-channeled fit between the parts, provides a self-fixturing that holds the two parts in exactly the proper position for joining. By extending the relief pattern around substantially the entire lateral periphery of the surface, the relief pattern centers the inserted surface within the recess. No separate fixturing or tack welding is required. The joining material fills the relief volume defined by the relief pattern, so that the joining material has a uniform thickness around the circumference of the joint. For brazing, the braze clearance gap may be made smaller than with conventional approaches in those situations where appropriate, improving capillary flow and strength of the joint. The size of the braze clearance gap between the parts may be established precisely yet inexpensively, at any value over a range of values.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.